Greeks The Greeks made other significant contributions to medicine The number of effective medicinal plants came to be about 300-400 species Hippocrates(460-377 B.C. ), Aristotle(384-322 B.C. )and Theophrastus(372-287 B.C. )essentially started the science of botany In the 19th century, such compounds as quinine, strychnine, morphine, and ephedrine were isolated and studied Later(mostly in the twentieth century) many of the compounds were synthesized and some became available from that source